This description of an interactive instructional computer program in sentence combining for upper elementary and middle school students begins by summarizing the content of the program, which focuses on the instructional technique in which students are given two or more short simple sentences to combine into one longer, complex and/or compound sentence. An outline of the four lessons presented by the program--coordinate predicates, coordinate adverbs and predicate adjectives, coordinate direct objects and predicate nominatives, and three kernel sentences containing the syntactic structures presented in the first three parts--is followed by a description of the structure of the individual lessons, including branching that occurs in response to student answers and the procedures that terminate the program. A discussion of some of the problems involved in developing highly interactive instruction for teaching composition on a microcomputer, and a list of nine references conclude the paper. (LMM)